Gather seed from a Buphthalmum speciosum plant in late summer once the seed heads dry out. Store the seed in a dry, darkened spot until the following spring.
Prepare a bed for the Buphthalmum speciosum seeds once the soil warms to 68 degrees F. Loosen the soil to a depth of at least 4 inches. Use a handheld soil cultivator for small areas and a rotary tiller for large field plantings.
Moisten the soil to a depth of 4 inches using a garden hose or oscillating sprinkler, depending on the size of the planting.
Sow the Buphthalmum speciosum seeds 1/2 inch deep. Space the seeds 24 inches apart.
Water the Buphthalmum speciosum seeds whenever the soil feels dry at a depth of 1/2 inch, but do not worry if the soil dries out slightly between waterings.
Watch for sprouting in four to eight days. Maintain moisture more rigorously for the first three weeks following sprouting by watering the plants daily to a depth of 1/4 inch. Decrease water to 1 inch every five days after that.